unit: Enable DNS

Avoid allocating in dns_init by enabling random source port.

test/unit/core/test_mem.c

@@ -6,9 +6,6 @@
 #if !LWIP_STATS || !MEM_STATS
 #error "This tests needs MEM-statistics enabled"
 #endif
-#if LWIP_DNS
-#error "This test needs DNS turned off (as it mallocs on init)"
-#endif
 
 /* Setups/teardown functions */
 

test/unit/core/test_pbuf.c

@@ -6,9 +6,6 @@
 #if !LWIP_STATS || !MEM_STATS ||!MEMP_STATS
 #error "This tests needs MEM- and MEMP-statistics enabled"
 #endif
-#if LWIP_DNS
-#error "This test needs DNS turned off (as it mallocs on init)"
-#endif
 #if !LWIP_TCP || !TCP_QUEUE_OOSEQ || !LWIP_WND_SCALE
 #error "This test needs TCP OOSEQ queueing and window scaling enabled"
 #endif

test/unit/lwipopts.h

@@ -51,9 +51,13 @@
 #define LWIP_HAVE_LOOPIF                1
 #define TCPIP_THREAD_TEST
 
-/* Enable DHCP to test it, disable UDP checksum to easier inject packets */
+/* Enable DHCP to test it */
 #define LWIP_DHCP                       1
 
+/* Enable DNS, with random source port to avoid alloc in dns_init */
+#define LWIP_DNS                        1
+#define LWIP_DNS_SECURE (LWIP_DNS_SECURE_RAND_XID | LWIP_DNS_SECURE_RAND_SRC_PORT)
+
 /* Minimal changes to opt.h required for tcp unit tests: */
 #define MEM_SIZE                        16000
 #define TCP_SND_QUEUELEN                40